The invention lies in the field of fluid dynamics. In particular, the invention pertains to dynamically optimized leading edge structures for various applications such as watercraft propulsion propellers, stationary fluid propellers, aircraft propellers, and aircraft wings.
In a series of earlier patents, including U.S. Pat. Nos. 6,164,919; 6,168,384; and 6,095,457, I presented a novel concept for propeller blade configurations and airfoil and wing configurations. The concept provided for the surfaces of propellers and the like that had previously been rounded along a slight curve in one direction, to be shaped along a tangent or a sine function. That is, a propeller cross-section at any line substantially perpendicular to a longitudinal axis of the configuration would show a double-curved shape which can be best described with a sine function and/or a tangent function. The leading edges of those structures were of no concern to me at that time.
The earlier disclosures of U.S. Pat. Nos. 6,164,919; 6,168,384; and 6,095,457 are hereby incorporated by reference.
While my earlier patents provide considerable advantages in a variety of speed ranges, additional improvementsxe2x80x94even those improvements that are apparently very minorxe2x80x94may lead to further efficiency increases. Especially in light of the dwindling supplies or non-renewable energy resources, any increase in efficiency, of course, is beneficial.
It is accordingly an object of the invention to provide a novel, dynamically optimized, leading edge structure, which further minimizes the above-mentioned disadvantages of the heretofore-known devices of this general type and which proposes a novel principle in leading edge structure design that further decreases the hydrodynamic and aerodynamic drag of such structures. Improvements are measurable, by way of example, in a further improved thrust-to-drag ratio of propeller blades and the corresponding efficiency of propulsion propellers and stationary pump propellers.
With the foregoing and other objects in view there is provided, in accordance with the invention, a propeller configuration, comprising:
a rotatable hub defining an axis of rotation;
at least two blade structures attached to the hub substantially perpendicular to the axis of rotation;
each of the blade structures having a leading edge, a trailing edge, a forward surface extending from the leading edge to the trailing edge, and a rear surface extending from the leading edge to the trailing edge;
the leading edge extending from the hub outwardly along a line being describable with a continuously positive slope and a reversing second derivative, or a first rounding concave rounding and a second convex rounding.
In other words, the leading edge of each of the blade structures follows a curve having a concave segment and an adjoining convex segment, or a segment that is concave up followed by a segment that is concave down.
In accordance with an added feature of the invention, the curve of the leading edge starts from the hub substantially along a tangent line, curves along the concave segment, and merges into the convex segment leading to the periphery.
In accordance with an additional feature of the invention, the trailing edge of each of the blade structures follows a curve having a concave segment and an adjoining convex segment.
In accordance with another feature of the invention, the curve of the trailing edge starts from the hub substantially radially outward, curves along the convex segment, and merges into the concave segment leading to the periphery.
In accordance with a further feature of the invention, relative to a center line of the respective blade, the curve of the leading edge is defined by a function y=a sin x, where xe2x88x92xcfx80/2xe2x89xa6x less than xcfx80 in radians, a being a real number defining an amplitude of the curve of the leading edge.
In accordance with again an added feature of the invention, each of the blade structures is formed with a forward surface extending from the leading edge to the trailing edge, and a rear surface extending from the leading edge to the trailing edge;
the forward surface and the rear surface at the leading edge extending substantially parallel to and offset from the forward surface and the rear surface at the trailing edge, and converging smoothly at the trailing and leading edges to form a sharp leading edge and a sharp trailing edge.
In accordance with again an additional feature of the invention, the forward surface and the rear surface are defined by a function y=a cos x, where 0xe2x89xa6xxe2x89xa6xcfx80 in radians, x being approximately equal to zero at the leading edge and x being approximately equal to xcfx80 at the trailing edge, and a being a real number defining a given thickness of the blade structures.
In accordance with again another feature of the invention, the leading edge and the trailing edge are defined by a tangent function. Preferably, the width of the blade structures defined between the leading edge and the trailing edge varies with a distance from the hub, with a relatively narrower segment at the hub merging into a relatively wider segment distally from the hub.
With the above and other objects in view there is also provided, in accordance with the invention, a wing configuration for a fixed-wing aircraft. The wing configuration comprises:
a wing structure attached to a fuselage of the aircraft and projecting sideways away from the fuselage;
the wing structure having a leading edge defined by a forward traveling direction of the aircraft, a trailing edge, and a free end distally from the fuselage, the leading edge of the wing structure following a curve having a concave segment and an adjoining convex segment.
Similarly to the above-summarized propeller blade, the curve of the leading edge starts from the fuselage substantially colinear with a sidewall of the fuselage, curves along the concave segment, and merges into the convex segment leading to the free end.
In accordance with yet an added feature of the invention, the trailing edge of the wing structure follows a curve having a concave segment and an adjoining convex segment.
In accordance with yet an additional feature of the invention, as defined relative to a center line of the wing structure, the curve of the leading edge is defined by a function y=a sin x, where xe2x88x92xcfx80/2xe2x89xa6xxe2x89xa6xcfx80/2 in radians, a being a real number defining an amplitude of the curve of the leading edge.
In accordance with a concomitant feature of the invention, the leading edge and the trailing edge are substantially defined by a tangent function.
The term propeller, herein, refers to propulsion propellers and impellers, such as for water propellers and for aircraft propellers (propulsion props, turbine blades, helicopter blades), as well as to stationary propellers and impellers used in high-power fans (wind tunnels, high velocity fluid pumps) and stationary turbines.
The term wing pertains to fixed wings and airfoils for fixed wing aircraft as well as gliders and glider wings for helicopters and the like.
In summary, I have now found that certain additional dynamic advantages over the prior art can be gained from variations in the leading edges and trailing edges of fluidically exposed structures.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in dynamically optimized leading edge structures, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.